Hand cut roof

A Hand cut roof is defined as a roof that is formed on site from indiviual timber elements.

Traditional hand cut roofs are predominantly formed of common rafters that span from a ridge board to purlin (singlular or multiple) to eaves level. The purlin is usually supported from a high level binder, with notch to accept the purlin or it is supported off raking purlin props, bearing to notches in ceiling joists. Where a high level binder suppports the purlin, the binder is usually affixed back to a rafter pair, with the rafters being larger than the common rafters, due to the additional point load from the binder. Where purlin props support the binder, they bear -at an angle, perpendicular to the pich of the roof- into a notch set in a ceiling joist.

An alternative to the above is the support of timber purlins off timber trusses, set at suitable centres. The trusses however are not formed in-situ and are instead lifted into position, prior to "hand cutting" the remainder of the roof into place.

Purlins are typically "Scarf jointed" at the head of supports.

The aim of a traditional hand cut roof is to split forces into Horizontal and vertial components, so that primary supporting elements (Binder/ rafter pairs) or ceiling joists do not have to carry the full load in bending/ flexure, thus reducing section sizes.